The present invention relates to the field of hydraulic units such as axial piston pumps and motors. More particularly, this invention relates to a method of manufacturing slippers that are pivotally connected to the axial reciprocating pumping or motoring pistons in such hydraulic units. The method can be used to provide bimetal male or female slippers.
A slipper in a hydraulic pump or motor must at one end provide a relatively soft, wearable hydrostatic running and sealing surface and at the other end be relatively hard and strong enough to withstand the forces associated with swivelingly connecting to one of the pistons. Using different materials for the running surface and the rest of the slipper might help better meet these divergent requirements. However, a cost-effective functional design and method of manufacturing a bimetal slipper has thus far not been developed.
Therefore, a primary objective of the present invention is the provision of a cost-effective method of manufacturing a bimetal slipper.
Another objective of this invention is the provision of a method of manufacturing bimetal slippers that utilizes capacitance discharge welding and is adaptable to both male and female slippers.
Another objective of this invention is the provision of a method of manufacturing bimetal slippers that is robust and provides reliable slippers and piston-slipper joints.
These and other objectives will be apparent from the drawings, as well as from the description and claims that follow.
This invention relates to a method of manufacturing slippers that are pivotally connected to pistons in hydraulic units. The method can be used to provide bimetal male or female slippers.
To manufacture male bimetal slippers the steps include forming a stem having opposite first and second ends; rigidly affixing a ball on the first end of the stem to form a male slipper body; and capacitance discharge welding a wear pad to the second end of the stem. To manufacture female bimetal slippers the method includes forming a slipper body of a first material, the body having opposite first and second ends, the first end having a ball socket formed therein; and capacitance discharge welding a wear pad of a second material to the second end of the body.
Forming a pair of concentric annular projections on the second end of the stem or slipper body helps ensure the load carrying capacity, leak integrity and strength of the welded joint between the body and the wear pad. In the case of the male slipper, forming a central longitudinal lubrication passage through the stem and using the lower peripheral edge thereof, at the stem""s first end, as a seat for the ball also provides predictability for the process of welding the ball to the stem. The means and method disclosed herein result in low cost bimetal slippers.